The present application relates to vehicle technologies, and in particular, to technologies that assure safety of drivers and passengers in vehicles such as cars and buses.
Whiplash is a relatively common injury that occurs to a person's neck following a sudden acceleration-deceleration force, most commonly from motor vehicle accidents. The term “whiplash injury” describes damage to both the bone structures and soft tissues, while whiplash associated disorders (WAD) describes a more severe and chronic condition. Although whiplash is typically not a life threatening injury, it can lead to a prolonged period of partial disability. There are significant economic expenses related to whiplash that can reach a huge amount of money including: medical care, disability, sick leave, lost productivity, and litigation. Whiplash is most commonly caused by a motor vehicle accident in which a person is riding in a stationary or slow moving car that is struck by a vehicle from behind without notice. It is commonly thought the rear impact causes the passenger's head and neck to be forced into hyperextension as the seat pushes the person's torso forward—and the unrestrained head and neck fall backwards.
Despite advances in safety devices, neck injuries in traffic accidents, especially non-severe rear impact accidents, are still a serious and costly social problem. The high cost of whiplash injury has been extensively documented. The development of safety measures to reduce whiplash injuries has been the source of many research investigations. Most of these research projects tried to provide an understanding of head-neck kinematics during low energy rear-collisions. This led to the introduction of head restraints since the 1960's as a countermeasure to limit relative motion between the head and thorax, thereby reducing injuries.
However, the effectiveness of these devices in reducing automotive injury has been limited. This is thought to be caused by the incorrect position of the head restraint. The first generation (unadjustable) head restraints were not optimally placed considering human anthropometry to prevent relative head-neck motions although they may have enhanced head-neck relative motion during rear collision. After being introduced, adjustable head restraints were found usually not positioned correctly which made them inefficient. Besides, even when used in their optimal locations, they have a limited benefit in reducing injuries because their static behaviors are often not adapted to the occupants' head positions at the times of the impact events.
There is therefore a need for improved designs for the safety devices on vehicles.